HYLOBATIDAE: Gibbon Family
The 9 species of gibbons are found in Southeast Asia, Sumatra, Java and Borneo. Like the apes, gibbons lack an external tail and have a protruding jaw. The gibbons are agile, slender primates weighing between 11 and 28 lb (5 and 13 kg).
The gibbons are specialized arboreal forms very different externally from the great apes. They probably have the most remarkable adaptations of all mammals for rapid locomotion through trees. Gibbons use their extremely long hands to swing through the forest canopy and are spectacularly skilful climbers. All gibbons have long, slender hands, with the thumb deeply divided from the index finger. This gives additional flexibility. When standing upright the gibbon’s long arms touch the ground, so they are often carried above the head. Gibbons are primarily vegetarian, but will also eat a diet of insects, young birds and eggs. The male and female of the gibbon species are generally similar in size.
There are several subspecies of black, or crested, gibbons, occurring in various parts of Indo-China. The subspecies differ in details of fur coloration. The male black gibbon is slightly larger than the female and has a tuft of hair on the crown. The female is buff colored, sometimes with black patches.
This species used to be much more widespread than it is today; at one time it lived in much of southern China, and was found as far north as the Yellow River in eastern China. It has suffered considerably from the loss of its forest habitat to logging and agriculture. It has also been hunted for its meat, which is considered a delicacy by some Chinese people, and for its bones, which are prepared as a local medicine to treat rheumatism.
Wars in South-east Asia have helped throw this species into decline, so that it now numbers less than 2,500.
Like other gibbons, the crested variety moves around the treetops searching for fruit and tender leaves during the day. However, unlike any other species, crested gibbons sometimes live in polygamous groups, with one adult male sharing a territory with up to four adult females.
Male crested gibbons are black, while females are golden or grey-brown in colour. Females are born almost white, and only attain their adult colour at between 2 and 4 years of age.
Gibbons communicate with complex calls which help to maintain their pair bonds. The male has a throat sac, which acts as a resonating chamber to amplify his voice. Black gibbons feed on a variety of foods, mostly ripe fruit, buds, leaves and insects, although occasionally small vertebrates may also be eaten.
Distribution: South-eastern China, Hainan, north-western Laos and Vietnam.
Habitat: Tropical forest.
Food: Fruit, leaves and insects.
Size: 45 - 65 cm (18 - 26 in); 5 - 9 kg (11 - 20 lb).
Maturity: 8 - 9 years.
Breeding: Single young born every 2 - 3 years.
Life span: 25 years.
Range: S.E. Thailand.
Size: Body: 17 - 23 1/2 in (43 - 60 cm). Tail: absent.
The pileated, or capped, gibbons derive their common names from the black cap on the heads of both sexes. Like all gibbons, they are born white and the adult pigmentation gradually spreads over the body down from the head. By the time they reach sexual maturity male pileated gibbons are completely black, while the females are buff colored with a black cap.
Pileated gibbons are strongly territorial and males scream and shout abuse to one another across their territory boundaries, although they seldom fight. The males give startling, loud solo calls at or before dawn.
This species feeds on a mixed diet of leaves, buds, tree resin and insects.
Range: Mentawi Islands west of Sumatra.
Habitat: Hill and lowland rain forest.
Size: 45 - 65 cm (18 - 26 in); 6 kg (13 lb).
This species is found only on a few islands in the Mentawai group, near western Sumatra. Due to its restricted range and low numbers, it is classified as vulnerable by the IUCN. Like other gibbons, this species defends territories in the forest, the males advertising their presence and strength to rivals by singing just before dawn.
Kloss’s gibbon looks like а small version of the siamang and is very similar in its habits. It is the smallest of the gibbons. It is thought to represent the form and structure of ancestral gibbons. Strictly tree-dwelling, it leaps and swings in the trees with great dexterity and feeds on fruit, leaves, shoots and, perhaps, insects.
Family groups, each consisting of an adult pair and up to 3 offspring, occupy a territory and sleep and feed together. Females give birth to a single young.
Size: 45-65cm (18 - 26 in); 4 - 9 kg (9 - 20 lb).
Javan gibbons are found only on Java, where they have lost over 95 per cent of their original forest habitat in recent decades. As a result, it is estimated that only 250 adults remain, making this the world's rarest gibbon.
Size: 45 - 65 cm (18 - 26 in); 4 - 9 kg (9 -20 lb).
This gibbon has the most westerly distribution of all the gibbons, living as far west as Bangladesh. The white-browed gibbon is the only species of gibbon that can swim, while all other species avoid water. Although gibbons can walk upright, they almost never cross open ground on foot. This means that features such as rivers and open spaces will act as barriers to the spread of gibbon populations.
Range: Bangladesh, E. India, S. China, Myanmar.
Habitat: Hill forest.
Size: Body: 18 - 24 3/4 in (46 - 63 cm) Tail: absent.
The hoolock has the long limbs and the shaggy fur that is characteristic of gibbons. Males and females are thought to be about the same size. The adult males are blackish-brown in color and the females are yellow-brown. Newborn hoolock gibbons are grayish-white and gradually darken as they age to become black at a few months old. The female’s color fades at puberty, which occurs at about 6 or 7 years of age. The hoolock gibbon is almost entirely treedwelling. It sleeps in the trees and in the daytime it swings itself quickly and easily from branch to branch and tree to tree, searching for food. Fruit, leaves and shoots make up the majority of its diet, but it will also sometimes supplement this with spiders, insects, larvae and birds’ eggs.
Family groups, which comprise of a mated pair and their young, live together. Normally each family group feeds in its own territory, but several families may occasionally gather in the same feeding area.
The hoolock’s loud calls are an important form of communication both within its own group and between groups. Mating occurs at the start of the rainy season, and females each bear a single young, some time between November and March.
Lar gibbons live in small social groups consisting of an adult male and female, and up to four immature offspring. Like the siamangs, adult lar gibbons defend their territories from intruders by calling, often in duets with males and females alternating their calls. However, lar gibbons spend much more time calling than siamangs, making calls nearly every day.
Female lar gibbons are much less social than female siamangs and, although the males spend a lot of time showing apparent signs of affection such as embraces and grooming behaviour, the females rarely reciprocate. Males are probably more likely to lose their partners to competitors than siamangs, hence the greater amount of calling.
Lar gibbons sleep in the highest trees in the forest, usually those giants that emerge from the forest canopy. They almost never sleep in the same place from night to night, and this is thought to be a strategy to prevent predators, such as pythons and birds of prey, from learning their position.
All lar gibbons have white hands and feet, giving them their alternative name, the white-handed gibbon.
These gibbons inhabit the upper canopy of the rainforest, swinging confidently between branches using their hands. They are rarely seen on the forest floor.
Lar gibbons are incredibly agile and able to jump 15 m (50 ft) from tree to tree. Aside from swinging under the branches, they can also walk along them, extending their arms out to keep their balance. Their calls are very loud, and carry through the forest, amongst the cacophony of other sounds, helping to indicate their territory. The arboreal nature of these gibbons means they are particularly vulnerable to the effects of deforestation in the areas where they are still present.
Distribution: Occurs in Southeast Asia, in Myanmar (Burma), China and through Thailand and Malaysia to Indonesia, reaching south to the island of Sumatra.
Habitat: Lowland tropical forest.
Weight: Around 5.5 kg (12 lb); males are slightly larger.
Length: 45 - 50 cm (18 - 20 in).
Maturity: About 9 years for both sexes.
Gestation Period: 217 - 248 days.
Breeding: 1; weaning occurs at 1.5 years; females breed every 2 - 3 years.
Diet: Mainly fruit, also leaves and other vegetation, plus eggs and sometimes invertebrates and small vertebrates.
Lifespan: 25 - 30 years
This species is also called the white-handed gibbon, because of the colour of its fur here.
Colour can vary from black through shades of brown to fawn, with white fur around the face.
A lar gibbon may surprise a nesting bird, as its reflexes arc quick enough to grab it in flight.
The arms are long, allowing the gibbon to swing through trees. This method of locomotion, with the gibbon using its hands to grip the branches alternately, is called brachiation.